A study has revealed a surprising new way to diagnose depression: have patients look at pictures of their moms. Apparently depressed women show unique brain activity when looking at their mothers' photographs.

According to Wired, researchers ran fMRI scans on 28 young women, half of whom suffered from depression. In the scanner, they had the women look at pictures of friends, strangers, and their moms. When they viewed the friend and stranger pics, the women's brains acted pretty much the same. But when they looked at their moms, the depressed women's brains showed significantly greater activity in a region called the anterior paracingulate gyrus, which scientists think is responsible for regulating social emotions. The differences were large enough that scientists were able to use the brain scans alone to tell with 90% accuracy which of the women were depressed.

The researchers aren't sure why this effect exists. And it's unlikely that the test can be a widespread clinical diagnostic tool anytime soon — it's a lot more expensive to run an fMRI on someone than it is to ask them about their emotions. Still, it's interesting that depression appears to affect what happens in people's brains when they see their mother's image, but not images of other people. Writes Jonah Lehrer of Wired,

Although these subjects are adults, the maternal relationship remains a window into the murk of their mental illness, as the Viennese doctor surmised long ago. This doesn't mean our parents are responsible for our sadness –- it's too early to say if Philip Larkin was right about mum and dad –- but Freud was definitely on to something when he insisted that the maternal relationship be considered in the context of therapy.

Of course, these new fMRI results don't shed any light on how this relationship should be considered in therapy. As with any fMRI study, it's a bit hard to say how activity in a certain brain region translates into helping an actual person. It's also hard to imagine therapists and psych researchers focusing any more on the maternal relationship than they already do — as Lehrer points out, psychiatry and psychology have had mommy issues since Freud. Maybe as brain research continues to progress, though, we'll learn more about the anterior paracingulate gyrus and its role in depression. Then we might know why it "lights up" at certain photographs, and what that means for depressed people and their mothers.